1. Field of the Invention
The present invention relates to an ink jet head comprising a top plate having a plurality of grooves arranged for forming ink passages and having a recess section for defining a liquid chamber communicating with the ink passages, a base plate (or a substrate) for forming the plurality of ink passages and the liquid chamber in a state joined to the top plate, ejection energy generating elements placed on the base plate for discharging inks and a supporting member for supporting the base plate at a surface of the base plate opposite to the surface thereof on which the ejection energy generating elements lie, and further relates to an ink jet cartridge equipped with this type of ink jet head and to an ink jet apparatus.
2. Description of the Related Art
An ink jet type apparatus is made to let fly ink droplets from microscopic discharge openings made in an ink jet head to a record medium, thereby accomplishing desired recording.
As recording apparatus designed to make recording on a record medium such as paper, cloth, plastic sheets and OHP sheets, there have been proposed apparatus of various recording types such as a wire dot type, a thermal recording type, a thermal transfer type and an ink jet type. Of these types, an ink jet type recording apparatus (ink jet apparatus) is applicable to an output means of an information processing system, such as a printer serving as an output terminal of a copying machine, a facsimile, an electronic typewriter, a word processor, a workstation or the like, alternatively a handy or portable type printer to be set in a personal computer, a host computer, a disk unit, a video unit or the like, and has been put on the market.
Furthermore, among ejection energy generating elements to be provided in an ink jet head of the aforesaid ink jet apparatus for generating energy to discharge an ink from ejection openings, for example, there are a type of using an electromechanical transducer such as a piezo element, a type of emitting an electromagnetic wave such as laser to generate heat for discharging ink droplets by the generated heat and a type of heating a liquid by an electrothermal converting element including a heat-generating resistor for discharging ink droplets.
In the recent years, with the progress of software and computers, the ink jet apparatus has been required to output color images, so that an ink jet head thereof has been designed to conducting the coloring processing according to these circumstances. The means employed currently therefor includes a multiple color head constructed by assembling single-color heads and further includes a multi-color head depending upon the ink jet head manufacturing method.
In addition to this coloring situation, a high fineness of the image output is also required, so that the ink jet type has been made to realize a higher fineness and a higher image quality through higher printing density and ink concentration variation.
Referring to FIGS. 3 to 8, a description will be given hereinbelow of one example of the aforesaid ink jet head.
FIG. 3 is an exploded perspective view schematically showing one example of an ink jet head applicable to the aforesaid ink jet type, and FIG. 4 is a perspective view showing a state in which the ink jet head shown in FIG. 3 is assembled.
Furthermore, FIG. 5 is a top view showing the ink jet head of FIG. 4 when viewed from an ejection opening arranged surface, and FIG. 6 is a cross-sectional view showing the ink jet head of FIG. 4, taken along a line A-Axe2x80x2 in FIG. 4, FIG. 7 is an enlarged view showing a joint portion between a base plate and a supporting member in FIG. 6, and FIG. 8 is a detailed illustration of a portion indicated at B in FIG. 6.
In the illustrations, reference numeral 3 represents a base plate, with a conventional base plate being commonly made of a silicon. On the base plate 3, there are provided a plurality of ejection energy generating elements (for example, electrothermal converting elements) 7 for ejection of inks. The base plate 3 is joined to a top plate in which grooves for forming a plurality of ink passages 9 and a recess section for forming a liquid chamber 10 are made according to a molding technique or the like, thereby defining the ink passages 9 and the liquid chamber 10. For sealing, a sealing material (not shown) is placed around the ink passages 9 and the liquid chamber 10 defined by the top plate 2 and the base plate 3 to prevent the occurrence of short-circuit by the flow of the ink to electrical junctions due to the ink leakage. Additionally, an orifice plate 16 having ink ejection openings 8 is integrated with the top plate 2. The base plate 3 and the top plate 2 are fixed to each other in a state pressed by a pressing member such as a spring. Still additionally, a supporting member 13 is installed on a surface of the base plate 3 opposite to the surface thereof on which the ejection energy generating elements 7 exist. Furthermore, numeral 4 depicts a wiring substrate connected electrically through lead wires to the ejection energy generating elements 7 disposed on the base plate 3, and the wiring substrate 4 is fixedly secured to the supporting member 13 by a UV adhesive 11 applied onto a V-shaped groove having a V-like configuration in cross section and made in a surface of the supporting member 13 coming into contact with the wiring substrate 4. Still furthermore, numeral 6 denotes a contact pad for communicating an electric signal from the ink jet apparatus to the wiring substrate 4, which is placed on the wiring substrate 4. The aforesaid sealing material is also used for the electrical junctions between the base plate 3 and the wiring substrate 4 to protect them by the prevention of ink adhesion.
In the ink jet head thus constructed, it is preferable that the plurality of ejection energy generating elements disposed on the base plate and the plurality of ink passage grooves made in the top plate are aligned accurately with each other. Accordingly, there is a need to assemble the top plate and the base plate with high precision, and it is desirable that the top plate and the base plate are joined smoothly in parallel with each other for excellent ink impact.
That is, in the case in which the base plate and the top plate are not joined smoothly in parallel with each other because the base plate is distorted with respect to the top plate or because the base plate is largely tilted relative to the top plate, of the ink passages defined by joining the base plate and the top plate, a gap appears between the adjacent ink passages with respect to the base plate so that the ejection pressure developed by the ejection energy generating elements is dispersed to the adjacent ink passage. In such a case, if the ink ejection quantity varies at a poor adhesion portion of the ink passages defined by joining the base plate and the top plate or if meniscus vibrations occur, the ink ejection speed becomes unstable at recording or the impact accuracy drops to cause the printing to fall into disorder easily so that difficulty is encountered in achieving high-quality recording.
As mentioned above, for the top plate and the base plate to be joined smoothly in parallel with each other, a point is that the base plate and the supporting member for supporting the base plate are joined smoothly in parallel with each other. However, so far, there has been a case in which the base is not joined smoothly in parallel with the supporting member supporting the base plate, and this reason is that the base plate is distorted in the arranging direction of the ejection energy generating elements and the base plate is tilted with respect to the top plate.
Referring to FIG. 9, a description will be given hereinbelow of the case in which the base plate is distorted in the arranging direction of the ejection energy generating elements. FIG. 9 shows a state in which, in the case of the conventional supporting member made from aluminum, the supporting member and the base plate are joined to each other by a high-temperature cure of a thermal conductivity adhesive, viewed from the ejection opening arranging surface side.
In FIG. 9, the base plate 3 on which the ejection energy generating elements are disposed is joined to the supporting member 13 by the high-temperature cure of the thermal conductivity adhesive 12, and the cure temperature at this time is as high as approximately 120xc2x0 C. to 150xc2x0 C. Accordingly, since the linear expansion coefficient of the supporting member 13 made from aluminum is extremely larger as compared with the linear expansion coefficient of the base plate made of a silicon, the rates of the contraction of the supporting member 13 and the base plate 3 differ from each other when it is returned to the ordinary (room) temperature, and distortion can occur in the arranging direction of the ejection energy generating elements of the base plate as shown in FIG. 9.
In addition, in the case in which electrothermal converting elements are employed as the ejection energy generating elements provided on the base plate in meeting relation the ink passages, when the arrangement density of the electrothermal converting elements becomes high, the heat generated from the electrothermal converting elements increases at printing. Accordingly, depending upon the arrangement density of the electrothermal converting elements, the temperature of the surface of the base plate opposite to the electrothermal converting element arranging surface approaches 100xc2x0 C. Thus, also in the case in which the difference in temperature between the base plate and the supporting member is large at printing and non-printing at printing and non-printing, due to the difference in linear expansion coefficient between the base plate made of silicon and the supporting member made from aluminum, distortion can occur in the ejection energy generating element arranging direction of the base plate.
Furthermore, referring to FIG. 11, a description will be made hereinbelow of the case in which the top plate and the base plate cannot be joined smoothly in parallel with each other since the base plate is tilted with respect to the top plate as mentioned above. FIG. 11 is an enlarged illustration of a joint between the base plate in FIG. 6 and the conventional supporting member made from aluminum. Since, in a method of manufacturing the supporting member 13, the conventional aluminum-made supporting member 13 is pressing-processed, the so-called shear drop 14 signifying a rounded corner portion or the so-called burr 15 signifying a projection occurs as shown in FIGS. 10C and 10D. Assuming that the burr 15 occurs on a surface of the supporting member 13 coming into contact with the base plate 3, as shown in FIG. 11, the burr 15 produces a gap with respect to the base plate 3, and the distance between the base plate 3 and the supporting member 13 can be E1 greater than E2. Additionally, in such a case, since the distance from the base plate 3 to the supporting member 13 is not uniform, the thermal conductivity adhesive 12 gathers in the gap produced by the aforesaid projection, which makes it difficult to apply the thermal conductivity adhesive 12 evenly.
Accordingly, the present invention has been developed in consideration of these situations, and it is an object of the invention to provide an ink jet head capable of joining a base plate and a supporting member smoothly in parallel with each other so that a plurality of ejection energy generating elements provided on the base plate are accurately aligned with a plurality of ink passages made on a top plate to achieve a high-quality recording without the occurrence of poor ink impact on a record medium, and to provide a manufacturing method capable of producing the ink jet head at a high yield, and further to provide an ink jet cartridge equipped with the ink jet head and an ink jet apparatus equipped with the ink jet cartridge.
For achieving this purpose, in accordance with this invention, there is provided an ink jet head comprising a top plate having grooves for forming a plurality of ink passages in an arranged condition and a recess section for forming a liquid chamber communicating with the ink passages, a base plate for establishing the plurality of ink passages and the liquid chamber in a state joined to the top plate, ejection energy generating elements placed on the base plate for ejecting an ink, and a supporting member for supporting a surface of the base plate opposite to the surface thereof on which the ejection energy generating elements lie, wherein the supporting member is made of a ceramic burned material.
In addition, in accordance with this invention, there is provided a method of manufacturing an ink jet head including a top plate having grooves for forming a plurality of ink passages in an arranged condition and a recess section for forming a liquid chamber communicating with the ink passages, a base plate for establishing the plurality of ink passages and the liquid chamber in a state joined to the top plate, ejection energy generating elements placed on the base plate for ejecting an ink, and a supporting member for supporting a surface of the base plate opposite to the surface thereof on which the ejection energy generating elements lie, the method comprising a step of producing the supporting member by burning a ceramic.
According to this invention, since the difference in linear expansion coefficient between the ceramic burned material and the silicon forming the material of the base plate is considerably less than that between the silicon and the aluminum used so far, when the base plate and the supporting member are adhered to each other by a high-temperature cure and returned to the ordinary temperature, the contraction rates of the supporting member and the base plate become substantially equal to each other and the expansion rates of the supporting member and the base plate becomes substantially equal to each other even when the difference in temperature between non-printing and printing is large due to an increase in arrangement density of the electrothermal converting elements serving as the ejection energy generating elements, so that the supporting member and the base plate can be joined smoothly in parallel with each other. Additionally, since the supporting member has no shear drop nor burr and has a uniformly formed burned surface, the supporting member and the base plate can joined smoothly in parallel with each other so that the thermal conductivity adhesive can be applied evenly onto a portion between supporting member and the base plate. Thus, this invention can solve the above-mentioned problems.